Threaded bushing for armored cable



June 2, 1931. GINSBURG 1,808,542

THREADED BUSHING FOR ARMORED CABLES Filed April 5, 1929 Hennj Gnsbur INVENTOR m ATTORNEY Patented June 2, 1931 PATENT OFFICE HENRY GINSBURG, OF NEW YORK, N. Y.

THREADED BUSHING roiz. ARMORED CABLE I Application filed April 5, 1929. Serial No. 352,639.

This invention relates to a protective bushing or ferrule for the end of armored electrical cable and has reference particularly to a threaded bushing of this character, which screws into the spirally wound metallic armor between the latter and the enclosed insulated conductors.

Protective bushings are well known in this art and the present invention is a further development of the particular type of bushing described and illustrated in United States Letters Patent No. 1,687,013, which relates to a split fibre bushing interposed between the insulated conductor or conductors and the interior of the metallic sheath, whereby all cutting action by the sharp edges or burrs formed in severing the metallic sheath or armor is avoided. The bushing in this arrangement is a split cylindrical member having its wall perfectly smooth and possibly slightly tapered, the

wall being first opened along the split and' disposed about the insulated conductor and thereafter slid along the latter until fully 2 inserted in the end of the armored cable.

The bushing just described, while it provides a perfect protective element in itself,

has the disadvantage of working its way out of position, due no doubt, to the fact that 30110 positive connection exists between the metallic sheath and the bushing, other than the frictional engagement between the smooth side of the ferrule and the adjacent interior wall of the armor.

The present invention therefore, succeeds in remedying this objectionable condition, and has for its object to provide a bushing or ferrule, either split or continuous, with a thread or threads corresponding in pitch 4 to that found in the spirally wound strands of the metallic armor about the conductors, the ferrule being disposed over the latter and inserted into the end of the sheath by catching the thread or threads of the bushi9 ing into the concave windings of the armor and then turning it until properly seated in the end of the latter.

One embodiment of my invention is described in the following specification, set forth in the claim, and illustratively exemplified in the accompanying drawings, in which, Figure 1 is a substantially longitudinal sectional view taken through an armored cable and protective bushing; Figure 2 is a perspective view of the bushing itself; Figure 3 is a side elevational view of the end of an armored cable and bushing partly inserted therein; and Figure 4 is a side elevational view of a bushing made of a continuous piece of fibre.

Referring to the drawings, 10 denotes the metallic armor or sheathing which is made of ,a spirally wound metal strip in any well known manner. The type of strip or strips which lends itself more readily to thepresent invention is one in which the strips are concave in transverse section on their inner face. This gives to the armor when properly wound, a decided interior spiral thread or threads. Within the sheath one or more insulated conductors 11 are disposed, the conductors being carefully wrapped in coils of paper strips 12, which may be removed for a short distance into the cable to allow space for a protective bushing 13.

The bushing is made up preferably of an insulating material such as .fibre, although it may be of metal if desired, because itsmain function is to provide a protective lining and end for the ragged end of the severed armor 10. In the embodiment illustrated in Figures 1, 2 and 3, the bushing is made from a flat strip of fibre curled about on itself to form a cylindrical portion 14, which is provided with an exterior thread or threads 15 pressed outwardly from the body of the portion 14. The material at one end of the bushing is flared outwardly to form a flange 16 which facilitates inserting the bushing into the end of the sheathing 10 because it affords a grip for the fingers o the operator, and which abuts againstthe end of the armored sheath to provide a smooth surface for the conductors lland avoids possibility of the insulation thereof being injured by the sharp edges at the end of the metal sheath.

The bushing may be cast in one continuous piece as illustrated in Figure 4 in which case no split is required.

To insert a bushing according to the present invention, the armored. cable is prepared in the usual way by releasing a small amount of the paper covering 12, thereafter placing the bushing 13 on the conductors 11' either by spreading the bushing or by slipping the same over the ends of the conductors. The cylindrical portion of the bushing is purposely made slightly tapered, so as to facilitate the entrance into the end of the armor.

Having once entered the space between the conductors 11 and sheath 10, the bushing is readily driven home by screwing the threads into the spiral lines of the metal sheathin until the flange 16 engages against the en of the armor'as illustrated in Figure 1.

Having now described my invention, What I claim and desire to secure by Letters Patent is :1

In combination, an armored electric cable comprising insulated conductors and a spirally Wound protective metal covering, the

- latter being formed of a metal strip which is substantially concave in transverse section on its face ad acent the lnsulated conductors, whereby the winding of the strip forms a spiral interior thread in the covering, and a threaded bushing to screw into the said interior thread of the covering between the latter and the insulated conductors, said bushing comprising a longitudinally divided slightly tapered cylindrical member having an exterior spiral thread to engageithe spiral thread in the covering and a flanged end to abut the end of the covering and form a protection for the insulation of the conductors.

In testimony whereof I aflix my signature.

HENRY GINSBURG. 

